adjust DrRacket's errortrace stack printer window so that it removes adjacent entries that have the same stack location and instead just says "skipped N duplicate frames" in the window
adjust DrRacket's errortrace stack printer window so that it
removes adjacent entries that have the same stack location
and instead just says "skipped N duplicate frames" in the
window

closes PR 12682

mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket